1. Field of the Invention
The present invention relates generally to a data transmitting apparatus and method in a mobile telecommunication system supporting multimedia service, and in particular, to an apparatus and method for transmitting data in a single format or in a double format.
2. Description of the Related Art
In general, a conventional CDMA (Code Division Multiple Access) mobile telecommunication system such as IS-2000 supports voice service only. To meet the users' growing demands, mobile communication technology has been developed to provide data service. A so-called HDR (High Data Rate) system supports only high rate data service. In other words, the conventional mobile communication systems support either voice service or data service alone, even though it may be desirable to support both services need simultaneously. Therefore, there is a need of a mobile telecommunication system capable of additionally supporting data service as well as the conventional voice service.
In order to satisfy the requirement, the mobile telecommunication system has been evolved to support service including the voice and data services using the same frequency band. More specifically, voice service is provided to a plurality of users in CDMA, whereas data service is supported basically in time division and CDMA is adopted in time slots assigned to a particular user. In such a system, data transmission occurs on a PLP (Physical Layer Packet) basis and a PLP can be constructed in a single format or a double format for the same data rate.
An increase in the size of an encoding block also increases a gain from turbo interleaving and channel interleaving. For the same data rate, better reception performance can be expected from transmission of a double-formatted PLP than from transmission of a single-formatted PLP. However, this characteristic is ensured only under a good mobile telecommunication channel environment where a sufficient gain can be obtained from turbo interleaving and channel interleaving. In other words, data transmission in the double format may increase a packet error probability as compared to data transmission in the single format.
Concerning data service, ARQ (Automatic Repeat request) is used to ensure a QoS (Quality of Service) at or above an acceptable level. As an increased packet error probability increases the number of retransmissions in ARQ, data transmission efficiency is decreased. Considering data transmission efficiency for a particular user and in the whole system, it is preferable to transmit data in the single format under an unstable, bad channel environment.